Celsius to Fahrenheit calculator
Water freezes at 0 °C, which is 32 °F: enter a value, say whether it is Celsius or Fahrenheit, and see both scales side by side. Handy for forecasts, oven settings, lab notes and worksheets. Free in your browser.
- Free
- Runs in your browser
- No sign-up
- Your data stays on your device
Run — free
Worked example
- Temperature magnitude to convert
- 0
- From
- Celsius
- Result
- 32
- To
- fahrenheit
- Celsius
- 0
- Fahrenheit
- 32
Converting between Celsius and Fahrenheit is one of the most common temperature tasks online: weather apps report °F while science labs, cooking metric recipes, school worksheets, and European product specs use °C.
What Celsius ↔ Fahrenheit conversion means and which inputs to send
Celsius and Fahrenheit are linear temperature scales with different zeros and degree sizes. Zero degrees Celsius is the freezing point of water at standard pressure; thirty-two degrees Fahrenheit is the same physical point. One hundred degrees Celsius is the boiling point of water on the same basis; two hundred twelve degrees Fahrenheit is its counterpart.
The exact relationships are F equals C times nine divided by five plus thirty-two, and C equals F minus thirty-two times five divided by nine. Search intent clusters around phrases such as celsius to fahrenheit calculator, convert C to F, fahrenheit to celsius converter, temperature conversion °C °F, and free online C to F tool. People want a numeric answer they can check against a weather report, a lab notebook, a cooking recipe, or an automated test—not only a reminder that the formula exists.
Both scales are always present so you never have to invert the result by hand. The calculator does not introduce kelvin or rankine; it stays focused on the everyday C↔F pair that dominates consumer and school searches.
Practical use, limits, pricing, and delivery channels
Use the browser tool when you want an immediate Celsius to Fahrenheit or Fahrenheit to Celsius check while reading a forecast, converting a recipe temperature, grading a worksheet, or verifying a sensor reading before you log it. Common landmarks are free to recall for sanity checks: zero Celsius is thirty-two Fahrenheit, one hundred Celsius is two hundred twelve Fahrenheit, and negative forty is the same on both scales. Results are fully deterministic: the same value and from always yield the same celsius, fahrenheit, result, formula, and method labels.
There is no language model, no external meteorology service, and no randomness, so the capacity is safe to pin in continuous-integration checks and reproducible lesson materials.
What you can do with it
Cooking and process recipes
Map oven and process temperatures between metric and imperial recipe cards without reimplementing the linear formulas in every app.
FAQ
How do I convert Fahrenheit to Celsius?
Send value and from set to fahrenheit (or F).
What happens if the temperature is not a number?
Non-numeric strings, missing value, NaN, and Infinity are rejected and those calls are not charged.
Is the Celsius to Fahrenheit calculator free?
The browser tool runs free on your device.
What is −40 °C in Fahrenheit?
Negative forty is the same on both scales: −40 °C equals −40 °F. Send value −40 with from celsius to confirm both fields.
Does it also convert to kelvin?
No. It stays on the everyday Celsius and Fahrenheit pair and always shows both scales, so you never invert the result by hand. For kelvin or Rankine you need a broader temperature converter.
Related tools
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/thermo/celsius-fahrenheit \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"value":0,"from":"celsius"}'const res = await fetch("https://api.kit.forhosting.com/thermo/celsius-fahrenheit", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"value": 0,
"from": "celsius"
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/thermo/celsius-fahrenheit",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"value": 0,
"from": "celsius"
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/thermo/celsius-fahrenheit", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"value":0,"from":"celsius"}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"value":0,"from":"celsius"}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/thermo/celsius-fahrenheit", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"value": 0,
"from": "celsius"
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "thermo.celsius_fahrenheit",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |
Technical notes
What Celsius ↔ Fahrenheit conversion means and which inputs to send
Delivering value, from, to, celsius, fahrenheit, result, formula, and method as JSON makes the output easy to paste into notes, diff in continuous integration, or reuse across languages without reimplementing the arithmetic.
How this calculator validates input and applies the linear formulas
Numeric strings that parse cleanly to finite numbers are accepted so forms and CSV-style pipelines can pass temperatures without an extra cast. After validation, if the source is Celsius the engine computes Fahrenheit with F equals C times nine-fifths plus thirty-two; if the source is Fahrenheit it computes Celsius with C equals F minus thirty-two times five-ninths. There is no weather lookup, no locale-dependent formatting of the unit symbols, and no stochastic step; this is pure linear scale conversion from the two known quantities. Send a JSON body with required fields value and from. The value must be a finite number: missing fields, empty strings, non-numeric text such as words or mixed units, NaN, and Infinity all fail immediately with invalid_input before any result is returned, and failed validation is not charged. Aliases are supported: temperature, temp, and t for value; unit, scale, and from_unit for the source scale. The from field accepts celsius, C, c, °C and fahrenheit, F, f, °F in a case-insensitive way; unknown scales are rejected as invalid_input. Results are rounded to a stable decimal precision so the same input always yields the same JSON across JavaScript engines. The same pure function powers the free in-browser tool and the API path so browser checks and server goldens stay aligned.
Practical use, limits, pricing, and delivery channels
Each successful request is one billable item at $0.002; failed validation does not consume balance. Wire the endpoint into weather widgets, cooking converters, contest answer checkers, or preprocessing steps where you already prefer explicit domain errors—such as rejecting a non-numeric temperature string—over opaque black-box widgets that cannot explain why a bad input was refused.
Integration use cases
Weather and travel temperature checks
Convert forecast or city temperatures between °C and °F for travelers, support scripts, and mobile widgets that need stable dual-scale JSON.
Homework and lab worksheets
Students and graders confirm C↔F pairs with clear invalid_input rejection when a field is missing or the temperature is not numeric.
Technical questions
How do I convert Celsius to Fahrenheit with this calculator?
Send value and from set to celsius (or C) to thermo.celsius_fahrenheit. The response returns fahrenheit (and result) using F = C × 9/5 + 32.